2008-2014 WRX/2008-2017 STi Street Series Air/Oil Separator

The Subaru EJ engine has 3 ports that vent crank pressure: one on each cylinder head and another on the top of the block. Each engine vent port receives its own connection to the AOS. By giving each engine port its own entrance to the AOS we have allowed for more effective and faster excavation of crankcase pressure. Additionally, this reduces overall system pressure. With a 4" OD and 5.75" height, the AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make without having to worry about the AOS overfilling.

As the air makes its way through the multi-stage baffle system, gravity pulls oil from the air. By increasing the overall volume of the breather opening on the top of the AOS, we have drastically decreased the exit velocity of the crankcase vent (CCV) stream. The slower velocity leads to greater oil separation from the pressure stream. A total of 9 mounting holes enable the breathing port a full 180° of rotation. On the bottom, a thick Viton o-ring seals the can. Every o-ring in our AOS is formed from Viton which offers superior temperature and chemical resistance. The bottom of the AOS is shaped like a snail, redirecting positive crank pressure into the same swirl pattern produced by the 3 side ports. Allowing maximum oil drainage while separating oil from the air in all the venting ports. The back plate of the AOS features a unique coolant routing system that heats the entire AOS to the same temperature of the engine. This maximizes the evaporation of any water collecting inside of the can. The hotter the AOS, the less water will collect inside and mix with the oil.

The AOS arrives completely assembled and ready for immediate installation. However, the entire unit can be broken down for cleaning. With a single allen wrench, you can remove 4 bolts and the AOS easily separates into individual pieces. The AOS drain port is able to be rotated for ease of installation. All fittings supplied with the AOS are anodized aluminum and feature Viton sealed ORB fittings. The supplied coolant hose is built to SAE 20R3 standards. It will withstand coolant temperatures of +257°F. The oil vapor hose is designed to withstand oil and fuel vapors, exceeding SAE J30R7 standards. The center bracket allows for adjustable mounting. If your engine bay changes, you can easily change how and where you mount the AOS. A single laser-cut mounting bracket is included that fits nearly all applications and configurations. A laser cut harness relocation bracket is also included. The bracket allows the engine harness connector to be moved forward for additional clearance.

Features

AOS Top - Dual Breather Port Rotation For Install Ease

AOS Top - Greater Pressure Stream Oil Separation

AOS Body - Large Billet Aluminum Design

AOS Body - Various Powdercoat Finishes Available

AOS Body - Approximate 1 Liter Holding Capacity

AOS Body - Integrated 3 Port Billet Hose Barbs

AOS Bottom - Unique Baffling Controls Crankcase Pressure

AOS Bottom - Returns Oil To The Engine

AOS Bottom - No Maintenance or Manual Draining Required

Ready to Install - Includes Hardware, Lines, and Fittings

PLEASE NOTE

IAG recommends the STREET SERIES AOS for ALL cars running E85 or high-ethanol fuel blends

References

Warranty

IAG Performance Warranty

2008-2014 WRX/2008-2017 STi Street Series Air/Oil Separator

The Subaru EJ engine has 3 ports that vent crank pressure: one on each cylinder head and another on the top of the block. Each engine vent port receives its own connection to the AOS. By giving each engine port its own entrance to the AOS we have allowed for more effective and faster excavation of crankcase pressure. Additionally, this reduces overall system pressure. With a 4" OD and 5.75" height, the AOS has an approximate 1 liter of holding capacity. The larger the AOS, the more power you can safely make without having to worry about the AOS overfilling.

As the air makes its way through the multi-stage baffle system, gravity pulls oil from the air. By increasing the overall volume of the breather opening on the top of the AOS, we have drastically decreased the exit velocity of the crankcase vent (CCV) stream. The slower velocity leads to greater oil separation from the pressure stream. A total of 9 mounting holes enable the breathing port a full 180° of rotation. On the bottom, a thick Viton o-ring seals the can. Every o-ring in our AOS is formed from Viton which offers superior temperature and chemical resistance. The bottom of the AOS is shaped like a snail, redirecting positive crank pressure into the same swirl pattern produced by the 3 side ports. Allowing maximum oil drainage while separating oil from the air in all the venting ports. The back plate of the AOS features a unique coolant routing system that heats the entire AOS to the same temperature of the engine. This maximizes the evaporation of any water collecting inside of the can. The hotter the AOS, the less water will collect inside and mix with the oil.

The AOS arrives completely assembled and ready for immediate installation. However, the entire unit can be broken down for cleaning. With a single allen wrench, you can remove 4 bolts and the AOS easily separates into individual pieces. The AOS drain port is able to be rotated for ease of installation. All fittings supplied with the AOS are anodized aluminum and feature Viton sealed ORB fittings. The supplied coolant hose is built to SAE 20R3 standards. It will withstand coolant temperatures of +257°F. The oil vapor hose is designed to withstand oil and fuel vapors, exceeding SAE J30R7 standards. The center bracket allows for adjustable mounting. If your engine bay changes, you can easily change how and where you mount the AOS. A single laser-cut mounting bracket is included that fits nearly all applications and configurations. A laser cut harness relocation bracket is also included. The bracket allows the engine harness connector to be moved forward for additional clearance.

Features

AOS Top - Dual Breather Port Rotation For Install Ease

AOS Top - Greater Pressure Stream Oil Separation

AOS Body - Large Billet Aluminum Design

AOS Body - Various Powdercoat Finishes Available

AOS Body - Approximate 1 Liter Holding Capacity

AOS Body - Integrated 3 Port Billet Hose Barbs

AOS Bottom - Unique Baffling Controls Crankcase Pressure

AOS Bottom - Returns Oil To The Engine

AOS Bottom - No Maintenance or Manual Draining Required

Ready to Install - Includes Hardware, Lines, and Fittings

PLEASE NOTE

IAG recommends the STREET SERIES AOS for ALL cars running E85 or high-ethanol fuel blends

Warranty

Customer Reviews

Great product from IAG ofcourse, they never fail customers on their product! MAPerformace was pretty helpful over the phone if you have questions regarding your build or what "car parts" you should get to match your build goals. Honestly, AOS is the first thing a subie owner should buy for the longevity of your engine. Will definitely buy this again!

J

J.R.

IAG AOS

Excellent product!!! As to be expected from IAG everything fit perfectly. And best part my oil consumption went down a bit always a plus for a subie.

G

G.C.

Great for Longevity for STi

Now first thing first got Maperformance thank you in the part. The problem that I have with this is everything is held by zip ties which is by far the worst idea but honestly this install is time consuming and should have a video instead for the install not paper work like how we use to use a book before all data was invented. Hopefully now my car doesn't have to blow up like it did the first time being stock.
I don't suggest it as your first mod but I suggest you get it once you hit 10k and notice the oil lose and calculate how many times you have to top every month. Honestly it's about saving money after doing a oil change and stop buying a quart of oil. Also I think this sis something you should do yourself cause I brought the part for 400$ and then the labor to get it done is honestly foul meaning another $400.

E

E.

Great Product

I recieved the item within 4 days which is a reminder of why I shop with MaPerformance. Installed the AOS myself and it wasn't too bad. My recommendation when installing is to just be patient and make sure everything is connected and clamped up correctly. I am very happy I went with the IAG over other brands, as you do get what you pay for with IAG AOS being the best.

MAP Limited Lifetime Warranty

1.) All MAPerformance in-house fabricated parts include a Limited Lifetime Warranty for the Original Purchaser. This warranty only applies to the original purchaser and is non-transferrable. If the product fails it would need to be determined by MAPerformance that it is due to manufacturing defects in materials or workmanship.

2.) This does not cover normal wear and tear. Improper use, modification, or abuse voids this warranty. MAPerformance will not be held responsible for additional costs due to the failure of a product (cost of sale, towing, labor, etc.). Warranty claims must be submitted to MAPerformance for review.

3.) You must create a support ticket to acquire your return authorization number prior to returning the product.

4.) Warranty claims will not be honored if the product was not purchased through an approved dealer.

For warranty evaluation please create a support ticket via this form here.

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